DMARC-Filter: OpenDMARC Filter v1.4.2 delorie.com 61QAog2u1037712
Authentication-Results: delorie.com; dmarc=pass (p=none dis=none) header.from=cygwin.com
Authentication-Results: delorie.com; spf=pass smtp.mailfrom=cygwin.com
DKIM-Filter: OpenDKIM Filter v2.11.0 delorie.com 61QAog2u1037712
Authentication-Results: delorie.com;
	dkim=pass (1024-bit key, unprotected) header.d=cygwin.com header.i=@cygwin.com header.a=rsa-sha256 header.s=default header.b=BUDUItcd
X-Recipient: archive-cygwin AT delorie DOT com
DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 842944B9DB57
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=cygwin.com;
	s=default; t=1772103041;
	bh=ib3Gk4x6sSoz2v6qY4jidGmsEWEqz6InLNmn/ra1+JQ=;
	h=Date:To:Cc:Subject:References:In-Reply-To:List-Id:
	 List-Unsubscribe:List-Archive:List-Post:List-Help:List-Subscribe:
	 From:Reply-To:From;
	b=BUDUItcdOu7qnJ6VVV4Sucnxy/GP2F82l2qrwyUCisln3nESxjSw/88PiZsID2isH
	 mj9m1vTX34KFaMdbaYuM2OJfvx7dVMTdMePA0ATKpqFWqCeCkvYi8h6L7rx4EB5T6f
	 MZ/eCLFy1tmDIWaZXk6wCxseeQNsrEfQSXt7u/6g=
X-Original-To: cygwin AT cygwin DOT com
Delivered-To: cygwin AT cygwin DOT com
DMARC-Filter: OpenDMARC Filter v1.4.2 sourceware.org 324624BA2E0B
ARC-Filter: OpenARC Filter v1.0.0 sourceware.org 324624BA2E0B
ARC-Seal: i=1; a=rsa-sha256; d=sourceware.org; s=key; t=1772102993; cv=none;
 b=al2xSS9L1lQ29PtwZ19svEBP6owwgGS9HXbFJXIXZ3Ki0h0YMHfZWmvb+XWhkpjsi+MsH99Xbq6jE19MUs0tqDvuWcCwBShN9GZ90+lcnagKtoGDWDHM64TH9N+Xw7SOepe2DINYh/d0biboGjw/aqKz1NtcfnXMZEr7aRH2p14=
ARC-Message-Signature: i=1; a=rsa-sha256; d=sourceware.org; s=key;
 t=1772102993; c=relaxed/simple;
 bh=3e9XViDK9Mbxq23zIYBvUFDD0csmQB2NHvnU9A4VhyY=;
 h=DKIM-Signature:Date:From:To:Subject:Message-ID:MIME-Version;
 b=khOvhcv1dJ/yRCV1eUDgPs1l/QlxetxDPb9z3hbK8CxOJEUj0BFI3iR9unglOrC0f0KcYfz8OCQNcBXgw/1LY4xIFX2Llc+rQLCzDCkFWOx+xP0Kw5Xol+aH1Ld5Y6PE66vkhoxk5gjrqfd+/A5/jWvLfJS8jLq3xzimot4RRP0=
ARC-Authentication-Results: i=1; server2.sourceware.org
DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 324624BA2E0B
Date: Thu, 26 Feb 2026 05:49:50 -0500
To: KENNON J CONRAD <kennonconrad AT comcast DOT net>
Cc: KENNON J CONRAD via Cygwin <cygwin AT cygwin DOT com>
Subject: Re: Memmove causing program crashes, giving SIGTRAP in GDB(?)
Message-ID: <aaAlThh5aeSYylcW@xps13>
References: <547312365 DOT 1464244 DOT 1771958282029 AT connect DOT xfinity DOT com>
 <aZ7PrbisVR1R4A7v AT dimstar DOT local DOT net>
 <1670201592 DOT 1489273 DOT 1772043520008 AT connect DOT xfinity DOT com>
 <e91d8b5b-2690-4271-aa74-e6226440e33d AT SystematicSW DOT ab DOT ca>
 <1044918836 DOT 1507810 DOT 1772086967212 AT connect DOT xfinity DOT com>
 <1579472684 DOT 1508349 DOT 1772092747339 AT connect DOT xfinity DOT com>
 <aaABFf5iEowV1l7I AT xps13>
 <1148572549 DOT 1808180 DOT 1772097444036 AT mail DOT yahoo DOT com>
 <1901597260 DOT 1508573 DOT 1772100378936 AT connect DOT xfinity DOT com>
MIME-Version: 1.0
Content-Disposition: inline
In-Reply-To: <1901597260.1508573.1772100378936@connect.xfinity.com>
X-BeenThere: cygwin AT cygwin DOT com
X-Mailman-Version: 2.1.30
Precedence: list
List-Id: General Cygwin discussions and problem reports <cygwin.cygwin.com>
List-Unsubscribe: <https://cygwin.com/mailman/options/cygwin>,
 <mailto:cygwin-request AT cygwin DOT com?subject=unsubscribe>
List-Archive: <https://cygwin.com/pipermail/cygwin/>
List-Post: <mailto:cygwin AT cygwin DOT com>
List-Help: <mailto:cygwin-request AT cygwin DOT com?subject=help>
List-Subscribe: <https://cygwin.com/mailman/listinfo/cygwin>,
 <mailto:cygwin-request AT cygwin DOT com?subject=subscribe>
From: Glenn Strauss via Cygwin <cygwin AT cygwin DOT com>
Reply-To: Glenn Strauss <gs-cygwin DOT com AT gluelogic DOT com>
Content-Type: text/plain; charset="us-ascii"
Content-Transfer-Encoding: 7bit
Errors-To: cygwin-bounces~archive-cygwin=delorie DOT com AT cygwin DOT com
Sender: "Cygwin" <cygwin-bounces~archive-cygwin=delorie DOT com AT cygwin DOT com>

On Thu, Feb 26, 2026 at 02:06:18AM -0800, KENNON J CONRAD wrote:
> Yes, movsq requires addess alignment.  Memmove however is not supposed to require alignment as it should work for chars, ints, etc.  It should handle alignment requirements before calling movsq.  That is something I want to verify.

Yes, this should be handled by memmove(), but I encourage verification
of assumptions.  If the code is supposed to be aligned due to default
natural alignment, inlining of memmove() might optimize on that
information (although it shouldn't if you compile -O0)

If sanitizer is available, you can try compiling with
  -fsanitize=alignment

Cheers, Glenn

-- 
Problem reports:      https://cygwin.com/problems.html
FAQ:                  https://cygwin.com/faq/
Documentation:        https://cygwin.com/docs.html
Unsubscribe info:     https://cygwin.com/ml/#unsubscribe-simple